Thermally actuated circuit delay switch

ABSTRACT

A switch for lighting fixtures and the like which provides either immediate opening of the circuit when actuated or optionally a delayed opening by means of a bimetallic thermal element responsive to a thermistor.

United States Patent Inventor Donald J. Gardner 3741 Penbrook Lane 0 13, Flint, Mich. 48507 Appl. No. 84,416

Filed Oct. 27, 1970 Patented Oct. 19, 1971 THERMALLY ACTUATED CIRCUIT DELAY SWITCH 4 Claims, 7 Drawing Figs.

US. Cl 337/81, 337/88, 337/341 Int. Cl ..H01h 61/00, HOlh 7 III 6 Field ofSearch 337/72, 53,

[56] References Cited UNITED STATES PATENTS 1,698,548 1/1929 Kailfman 337/81 x 1,985,633 12/1934 Finizie.... 337/53 X 2,119,080 5/1938 Kennedy 337/81 2,852,640 9/1958 DeLancey 337/107 Primary Examiner-Harold Broome Attorney-Dennison, Dennison, Townshend & Meserole ABSTRACT: A switch for lighting fixtures and the like which provides either immediate opening of the circuit when actuated or optionally a delayed opening by means of a bimetallic thermal element responsive to a thermistor.

PATENTEDnm 191971 3.614.698

sum 2 [1F 2 INVENTORS DONALD J. GARDNER av WM ATTORN EYS THERMALLY AC'IUA'IEI) CIRCUIT DELAY SWITCH The present invention relates to delayed action power switches which respond to operation of a control to effect a delayed opening of a power circuit or at the option of the operator an immediate opening of a power circuit. Delayed operation of the switch is provided by a bimetallic thermal element responsive to a thermistor.

A power switch of this character can provide in a number of environments distinct advantages to' the control of electric lights, for example when to control an outside light for a residence, garage or other building, such a switch permits a person to move a switch control it its off position before leaving the area and then proceed away from the building before the switch turns out the lights. When installed in a bedroom, such a switch can pennit a user to move a switch control to an 06 position aiid then make his way into bed before the switch operates to turn out the light. By keeping a controlled light burning for a limited period of time after the switch has been manually operated to turn out the light, such a switch enables the user to avoid the hazard and inconvenience of having to move away from the switch in the dark after the switch control has been operated.

Prior switches of this character have tended to be impractical because of structural complexity, high manufacturing costs, lack of dependability, bulkiness, and other factors which have detracted from the advantages which may be gained from the use of such a switch.

One object of the invention is to provide a new and improved delayed action power switch wherein the bimetallic delay switching element is subject to the control of a thermistor instead of the more expensive wire-wound heaters commonly used.

Another object of the invention is to provide a new and improved delayed action power switch which may be turned off immediately if desired and is well adapted for general residential and similar usages, and having an inherent practicality by virtue of being well adapted for economical manufacture and having an inherent capability for operating dependably and eificiently in service.

Another object is to provide a delayed action power switch as recited in the preceding objects which occupies an very small space.

Another object is to provide a novel switch of small size adapted to be incorporated in a conventional electric lamp socket.

Another object is to provide a novel switch of small size adapted to be incorporated in a conventional wall-mounted switch housing.

Another object is to provide a novel switch connector plug of small size adapted to be plugged into an ordinary household power outlet socket in the manner of a conventional electric plug and serving to provide an efficient, dependable delayed action opening of the electrical circuit to the switch connector plug itself.

Another object is to provide a novel switch of small size adapted to be incorporated into an ordinary electrical extension cord in a manner to provide remote control of the apparatus deriving power via the electrical extension cord.

Another object of the invention is to provide a delayed action power switch of small size adapted to be incorporated into an ordinary electrical socket of the permanently installed variety or of the extension cord variety.

Another object is to provide a compact switch of the delayed action type as recited in the preceding objects which can be used as a replacement for conventional switches in the base of lamps or other objects to provide the improvement of a delay function to the object.

Another object is to provide a thennally actuated circuit delay switch which is economical to manufacture by virtue of its simplicity of assembly afforded by the minimal number of parts required and the inexpensive nature of the parts.

Another object is to achieve the objects previously recited by means of structure in which the working parts which effect the delayed opening of a circuit are confined essentially to a simple bimetallic element in cooperation with a thermistor.

Other objects and advantages will become apparent from the following description of the exemplary forms of the invention illustrated in the drawings, in which:

FIG. I is a schematic representation of the switch illustrating the electrical relation between the power source, controlled lamp, thermistor, bimetallic element and switching contacts.

FIG. 2 is a plan view of the switch assembly with cover removed on a mounting base showing the physical relationship of the parts forming the delayed action power switch.

FIG. 3 is a side elevation partly in section of the switch assembly depicted in FIG. 2.

FIG. 4 is an end elevation partly in section of the switch assembly and base illustrating the spring and ball latching apparatus for the switch contact actuating lever.

FIG. 5 is an exploded perspective of the switch assembly revealing the interrelationship of all the parts of the complete switch assembly.

FIG. 6 illustrates an alternate embodiment of the spring contact arm wherein the arm is fabricated to eliminate the need of a mounting bracket.

FIG. 7 illustrates an alternate embodiment of the switch assembly wherein the spring and ball contact arm latching means is replaced by a flat-formed spring.

Referring to the drawings in greater detail, FIG. 1 illustrates the electrical circuit of the invention in the normal nondelay on position. As the circuit is presented current flows from the power source 10 through terminal 11 to the electric lamp 12 then through the closed switch contacts 13 and 29 back to the power source 10. When the switch control knob is moved to the immediate off position, contacts 13 and 29 open breaking the circuit and the lamp is extinguished. When the switch is moved to the delayed off position, the contact between 13 and 29 is opened and contact 27 closes on contact 14, providing a path for current in parallel with the open switch contact 13 through the bimetallic element 15 to the electric lamp I2 such that the light will remain illuminated. Closing of contact 27 causes contact 16 to close on contact 25 due to the mechanical relationship and interconnection of contacts 14 and I6 and a path for current is thus provided through thermistor element 17. The thermistor 17 is in parallel with the lamp I2 and bimetallic element 15 so there will be no noticeable reduction in the brilliance of the lamp 12 when the thermistor is placed in the circuit. Current flowing through the thermistor 17 generates heat which causes the bimetallic element 15 to move, opening the contact at 14 and extinguishing the lamp. The mechanical interrelationship between contacts 14 and 16 is such that'when contact I4 is open by the effect of the bimetallic element 15 contact 16 is also opened and the bimetallic element is allowed to cool. As the bimetallic element cools contacts 14 and 16 are prevented from closing due to spring biasing means contained in the switch assembly, see FIGS. 4 and 8.

FIG. 2 illustrates the physical interrelationship of the three sets of contacts. Terminal 20 acts as a common point for contacts 25, 27 and 29 in that it is electrically and mechanically connected to a switch arm 22 and spring contact arm 23. When the knob 24 is rotated in a counterclockwise direction, contact 25 engages contact 16 closing the circuit through the thermistor 17 via the continuation of the conductive metal strap 26 which forms contact 16. The action of contact 25 against contact 16 forces the bimetallic contact I4 against contact 27 to provide a parallel path for current through the bimetallic element 16 to the lamp via terminal 21. As heat generated by the thermistor 17 is transmitted through the bimetallic element 15 it causes the bimetallic element I5 to warp toward contact 14, this releases the spring tension at contact 16 created by the contactand configuration of the conductive metal strap 26. Releasing this spring tension frees contact point 25 from the detent of contact 16 and the compressional tension of spring 28 returns contact arm 22 to the off position. Rotating the knob 24 in a clockwise direction causes contact 29 of contact arm 22 to engage contact 13 completing the circuit to the lamp via terminal2l. The contact am is held in this on position via the action of the ball 30 and spring 31 located in a bore 32 which extends part way through the switch base 33 which is formed of a nonconducting material and may be provided with mounting flange 19. The spring loaded ball 30 provides the latching action by the pressure it applies to the protrusion 34 located on the underside of contact arm 22 in the area of contact surface 29 (see FIG. 4). FIG. 7 illustrates an alternate embodiment wherein the spring 31 and ball 30 are replaced by a flat spring 90 having an arcuate cam surface 91 fonned at one end to cooperate with protrusion 34.

FIG. 3 illustrates a housing 35 over the switch assembly mounting base 33 wherein a bore 36 is provided in the top of the housing in which a grommet 37 is inserted for providing stabilizing support to the knob 24. This housing 35 may be in the form of a four-sided box or a two-sided bracket. FIG. 7 illustrates an alternate embodiment wherein the grommet 37 is replaced by a hollow sleeve 92 threaded on the outer periphery and having a flange 93 at one end. This sleeve is dimensioned such that it can be screwed through the bore 36 of the cover 35 and retained by the flange 9.3. A nut 94 is provided to secure the assembly to an object such as a lamp base.

FIG. provides additional details of the physical characteristics of the components utilized in the switch assembly. For instance, it can be seen that the knob assembly 24 consists of a shaft 40 with an enlarged circular head or disc 41 at one end to facilitate manual operation and a rectangular segment 42 formed at the other end to cooperate with the rectangular opening 43 formed in switch arm 22 such that as the knob 24 is rotated switch arm 22 will follow the knobs movements. A bore 44 is located in the center and along the longitudinal axis of the shaft 40 at the end having the rectangular segment. A spring clip 53 is provided in the bore 44 and cooperates with screw 45 to secure the knob assembly 24 and switch arm 22 to the switch mounting base 33 via the bore 46 provided in the base. In addition to mechanically securing the knob 24 and switch arm 22 to the base 33, screw 45 secures terminal to the switch base 33 and thus provides an electrical connection between tenninal 20 and switch arm 22. Terminal 20 is a conventional terminal having a bore 48 formed in one end and a wire-retaining spring clip formed in the other. Contact spring arm 23 is also secured to the base 33 by screw 45 which passes through a bore 50 located in the spring ann attaching bracket 51. The spring ann attaching bracket 51 is welded or otherwise secured to the base segment of spring arm 23; however, if desired, spring arm 23 can be formed such that the base segment is elongated and rotated perpendicular to the plane of the spring arm as illustrated in FIG. 7. This subassembly of component pans of the switch is assembled by threading the washer 47 on the screw 45 followed by terminal 20 which has an elongated end containing a bore 48' for mounting purposes. The screw 45 is then inserted through the bore 46 of base plate 33 and he bore 50 of spring arm attaching bracket 51. Nut 48 is threaded on screw 45 to electrically and mechanically secure terminal 20 and spring arm attaching bracket 51 to oppose sides of the switch base plate 33. A conductive washer 49 is provided between nut 48 and switch arm 22 to prevent binding of the switch arm and enhance electrical contact. Switch arm 22 is placed over screw 45 and knob 24 containing the spring clip 53 is pressed down on the screw until the rectangular segment 42 of the knob 24 engages the rectangular hole 43 of switch am 22. The spring clip 53 binds the threads of the screw 45 and secures the knob 24 and switch arm 22 to the assembly but does not prevent rotation of these parts.

Spring 28 is a partially extended coil spring which provides extension and compression biases for switch arm 22. It has a closed loop 54 formed at both ends and is affixed to the base 33 by a self-tapping screw 55 which passes through one closed loop and into a bore 56 provided in the base 33. The other end of the spring is fastened to spring arm 22 by a nut 57 and screw 58 by passing the screw 58 through the closed loop 54 of the spring 28 and the bore 59 provided in the spring arm 22. If

desired, screw may be replaced with a rivet or screw and nut.

The bimetallic assembly 15 is fastened in an L-shaped configuration wherein the longest length of the L is of bimetal construction and the shortest length is a continuation of one leaf. This short length 60 passes through a slot 61 in the base 33 and is bent 90 to form an attaching flange 62. A bore 63 is provided in the attaching flange for receiving terminal screw 21 which engages threaded bore 67 formed in the base plate 33. Extension 60 of the bimetallic element 15 is dimensioned sufficiently wide to prevent twisting of the bimetallic element 15 in the base plate. Additional rigidity is provided at the attaching end of the bimetallic element 15 by terminal strip 64 which is secured to the bimetallic element by a screw 70 and nut 71. The other end of terminal strip 64 passes through a slot 65 in the base plate 33. It is bent 90 after emerging on the underside of the base plate and secured to the base plate via terminal screw 1 1, the shank of which passes through the bore 66 provided in the terminal strip and engages the threaded bore 68 provided in the base plate. Thermistor 17 is a conventional cylindrical thermistor having a bore 79 through its center. It is mechanically secured to the bimetallic element 15 and terminal strip 64 by screw 70 and nut 71. A conductive washer 72 is provided to insure electrical contact of screw 70 with one end of the thermistor 17. An insulated sleeve 73 passes through the center of the thermistor 17, the bore 74 of terminal strip 64 and the bore 75 of bimetallic strip 15 to insure that screw 70 does not make electrical contact with the interior of the thermistor 17 or terminal strip 64 of bimetallic element 15. Insulating washers 76 and 77 are provided to insure electrical isolation of terminal trip 64, bimetallic element 15 and conductive strap 26. A flat washer 78 is provided to enhance electrical contact of the screw 70 and nut 71 with the conductive strap 26 which is mechanically but not electrically secured to the bimetallic element 15 by screw 70 and nut 71. The opposite end of the conductive strap 26, forming detent contact 16, is secured to the free end of the bimetallic element 15 via screw 80 and nut 81. The bimetallic element 15 and conductive strap 26 are electrically isolated by the insulating washer 82 which has a collar and a sleeve-type protrusion which fits into bore 83 of the bimetallic element 15 and insulating washer 84. Washer 85 is provided solely to protect the conductive strap 26 from the effects of tightening nut 81. If desired, screw 70 and nut 71 as well as screw 80 and nut 81 may be replaced by rivet-type fasteners. Also self-taping screws 1 1, 21 and 55 may be replaced with bolts and nuts.

Switch base 33 is constructed from a nonconductive material and its thickness is a function of the size of the components mounted thereon, such as spring 31. Therefore, when the switch assembly is utilized in a standard lamp socket, see FIG. 7, the spring 31 and ball 30 are replaced by a small flat spring member one end 91 of which is curved to provide the locking functions of the ball 30.

It is to be understood that in the description of this invention only a few of the various combinations which can be created have been given for the sake of simplicity in the disclosure. Thus while various combinations have in general been shown by simple sketches additional uses and combinations of the switch assembly which would be obvious to one skilled in the art are anticipated.

What is claimed is:

1. A delayed action switch comprising:

a nonconductive mounting base;

a switch arm having first and second electrical contact surfaces pivotally mounted to said base;

a first electrical contact rigidly mounted on said base and positioned apart but within the normal path of movement of said first contact surface of said switch arm for completing an electrical circuit therebetween;

a thermally responsive bimetallic element having first and second ends rigidly secured and electrically connected at said first end to said first electrical contact;

a first spring-biased electrical contact mechanically secured but not electrically connected to said second end of said bimetallic element and positioned apart of said second contact surface of said switch arm but within the normal path of motion thereof for completing a circuit therebetween;

a latching detent formed in one end of said first springbiased contact for cooperating with said second contact surface of said switch am for securing said switch arm in electrical continuity with said first spring-biased contact when said bimetallic element is not thermally warped;

a second spring-biased electrical contact having a contact surface formed at one end and the other end electrically connected to said switch arm and rigidly secured to said base, said contact surface being nonnally positioned apart from said bimetallic element but within the path of motion of said second end of said bimetallic element for completing a circuit therebetween when said bimetallic element is mechanically or thermally warped;

a first electrical terminal secured to said base for providing a common electrical connection between said delayedaction switch, a power source, and an electrical load;

a thermistor electrically connected to said first electrical terminal at one end and electrically connected to said first spring-biased connector at the other and positioned adjacent to said bimetallic element so that said bimetallic element will be thermally responsive to said thermistor;

a second electrical terminal secured to said base and electrically connected to said second spring-biased contact and said switch arm for providing electrical connection to said power source;

a third electrical tenninal secured to said base and electrically connected to said first electrical contact for providing an electrical connection to said electrical load;

a first spring secured at one end to said base and at the other end to said switch am for biasing said switch arm in a position where said first and second contact surfaces are not in contact with said first electrical contact and said first spring-biased electrical contact;

a second spring-biased means secured to said base for maintaining said first contact surface of said switch arm in electrical contact with said first electrical contact when said first spring is extended by rotation of said switch arm; and

manual control means for positioning said switch arm.

2. A delayed action switch as defined in claim 1 wherein said second spring-biasing means consists of:

a bore formed plurality through said switch mounting base;

a helical coil spring contained in said bore;

A cam surface formed on the mounting base side of said switch arm; and

a spheroid positioned on top of said helical spring for engaging said cam surface.

3. A delayed action switch as defined in claim 2 wherein said thermistor has a bore therethrough, said bimetallic element has a bore formed in said first end and said first electrical terminal has a bore formed in one end, an electrically conductive metallic strap formed as an extension of said first springbiased contact having a bore formed in the end opposite said first spring-biased contact mechanically but not electrically secured to said first end of said bimetallic element; a headed conductive screw inserted in said bores of said thermistor, said first electrical terminal, said bimetallic element and said conductive metallic strap such that said thermistor and said first electrical terminal are physically positioned to provide electrical contact between one end of said thermistor and said first electrical terminal.

4. A delayed action switch as defined in claim 3 and further including:

a cover for enclosing said switch assembly affixed to said base and having a bore through the upper side through which said control means protrudes, and

a bottom cover affixed to said base. 

1. A delayed action switch comprising: a nonconductive mounting base; a switch arm having first and second electrical contact surfaces pivotally mounted to said base; a first electrical contact rigidly mounted on said base and positioned apart but within the normal path of movement of said first contact surface of said switch arm for completing an electrical circuit therebetween; a thermally responsive bimetallic element having first and second ends rigidly secured and electrically connected at said first end to said first electrical contact; a first spring-biased electrical contact mechanically secured but not electrically connected to said second end of said bimetallic element and positioned apart of said second contact surface of said switch arm but within the normal path of motion thereof for completing a circuit therebetween; a latching detent formed in one end of said first spring-biased contact for cooperating with said second contact surface of said switch arm for securing said switch arm in electrical continuity with said first spring-biased contact when said bimetallic element is not thermally warped; a second spring-biased electrical contact having a contact surface formed at one end and the other end electrically connected to said switch arm and rigidly secured to said base, said contact surface being normally positioned apart from said bimetallic element but within the path of motion of said second end of said bimetallic element for completing a circuit therebetween when said bimetallic element is mechanically or thermally warped; a first electrical terminal secured to said base for providing a common electrical connection between said delayed-action switch, a power source, and an electrical load; a thermistor electrically connected to said first electrical terminal at one end and electrically connected to said first spring-biased connector at the other and positioned adjacent to said bimetallic element so that said bimetallic element will be thermally responsive to said thermistor; a second electrical terminal secured to said base and electrically connected to said second spring-biased contact and said switch arm for providing electrical connection to said power source; a third electrical terminal secured to said base and electrically connected to said first electrical contact for providing an electrical connection to said electrical load; a first spring secured at one end to said base and at the other end to said switch arm for biasing said switch arm in a position where said first and second contact surfaces are not in contact with said first electrical contact and said first spring-biased electrical contact; a second spring-biased means secured to said base for maintaining said first contact surface of said switch arm in electrical contact with said first electrical contact when said first spring is extended by rotation of said switch arm; and manual control means foR positioning said switch arm.
 2. A delayed action switch as defined in claim 1 wherein said second spring-biasing means consists of: a bore formed plurality through said switch mounting base; a helical coil spring contained in said bore; A cam surface formed on the mounting base side of said switch arm; and a spheroid positioned on top of said helical spring for engaging said cam surface.
 3. A delayed action switch as defined in claim 2 wherein said thermistor has a bore therethrough, said bimetallic element has a bore formed in said first end and said first electrical terminal has a bore formed in one end, an electrically conductive metallic strap formed as an extension of said first spring-biased contact having a bore formed in the end opposite said first spring-biased contact mechanically but not electrically secured to said first end of said bimetallic element; a headed conductive screw inserted in said bores of said thermistor, said first electrical terminal, said bimetallic element and said conductive metallic strap such that said thermistor and said first electrical terminal are physically positioned to provide electrical contact between one end of said thermistor and said first electrical terminal.
 4. A delayed action switch as defined in claim 3 and further including: a cover for enclosing said switch assembly affixed to said base and having a bore through the upper side through which said control means protrudes, and a bottom cover affixed to said base. 